The present invention relates generally to electrical switches and, more particularly, to a switch utilizing movable contacts and a printed circuit board as the switching element, having a guide member for the contact carrier mounted directly to the printed circuit board substrate.
One commonly used type of switch mechanism includes a set of sliding contacts which electrically engage a series of conductive paths printed on a circuit board substrate. Switch mechanisms of this type are often used, for example, in the automotive industry for headlamp and other control switches placed on a vehicle dash panel. The switch contacts are typically retained by a contact carrier and movement of the contact carrier, and therefore travel of the contacts with respect to the circuit paths, is controlled via a guide member which controllably engages the carrier. This guide member is typically formed separately from the circuit board and contains a projecting portion which extends upwardly through a suitable opening in the circuit board. This projecting portion is typically slidingly engaged by the contact carrier and thereby aligns the contacts with respect to the conductive paths, controlling the direction of travel. The contact carrier is further engaged by a means for causing movement thereof along the guide member, such as a pin whose movement is caused by rotation of a thumb wheel or actuation of another type of rotary or linearly sliding knob.
This control guide arrangement, however, may have several inherent drawbacks. Forming the guide member separately, typically as part of a protective housing which surrounds the switch mechanism, can negatively affect manufacturability. Holding closer to tolerances between the housing and other switch components is required and the assembly process is made more difficult. Repairability of the switch is also hindered by requiring replacement of a greater portion of the switch if a malfunction or damage to the switch occurs. Separately formed components also result in a larger resulting overall tolerance between the guide member and contact carrier, thus affecting part functionality and reliability as well as requiring more space.
This space requirement can be a problem since the design envelopes being made available for such switches in automobile dash panels are shrinking, with increasingly less space in the dash being devoted for such switches. Switch designers therefore often face the task of providing a functional and reliable switch mechanism in the smallest possible space. Therefore, there exists a need for a switch mechanism of this general type with a reduced space requirement. Such a switch must also be reliable, cost effective and facilitate ease of assembly.